import matplotlib.pyplot as plt
import numpy as np
import pandas as pd

# 透明度
x = np.linspace(-1, 1, 1000)
y = (1 - x ** 2) ** 0.5
# 透明度是[0,1]之间，不在范围会报错
plt.plot(x, y, x, -y, c='r', alpha=0.5)
plt.axis('equal')
plt.show()

